How many will be uninhabitable for months? Pipes and fresh-air tubing in a Financial District luxury apartment building this week. Photo: EPA

Downtown landlords and real-estate brokers need to come clean about how ruinous Hurricane Sandy was to the precious district below Chambers Street.

No, it wasn’t 9/11. Relatively few lives were lost. No buildings were completely destroyed and tenant relocations are supposed to be temporary.

But “temporary” in some cases will mean up to a year.

Water Street and Front Street, normally bustling office corridors, are eerily devoid of life. Entire retail blockfronts, like on the west side of Water Street north of Broad Street, remain shuttered.

Meanwhile, in a human uprooting that rivals parts of Staten Island and the Rockaways, residents of high-rise apartment buildings along and near West Street are homeless for the foreseeable future.

How many, exactly? Nobody knows.

The Financial District has been the city’s fastest-growing residential neighborhood, even while remaining the nation’s third-largest central business district. The hurricane is a wild card, though.

Although the real-estate industry and downtown advocates are pushing the line that the area will bounce back, it’s beside the point.

Of course it will come back. But maybe not as fast as anyone hopes.

Too many are in denial. Too much time’s being spent on long-term proposals to build sea walls around Manhattan, and precious little on today’s conditions.

Real-estate executives who know The Post as a stalwart believer in Downtown have asked me to put a positive face on the situation.

But there’s no positive face to nearly 30 million square feet of prime office space standing temporarily empty, or to the mess that much of the Wall Street district’s eastern side remains, two weeks after the storm.

Yes, progress has been made: Some office addresses have reopened and others, like giant One New York Plaza, are expected to reopen as early as next week. The Andaz Hotel is back; so are Delmonico’s and Harry’s restaurants.

But the remaining flood carnage has yet to be tabulated. In a climate of ignorance, upbeat forecasts of a swift turnaround help no one.

What’s needed is unflinching quantification of how many office buildings are closed, how many residents displaced from their homes, how many stores and restaurants knocked out.

Only from comprehensive, credible data — as was available almost immediately after 9/11 — can decisions responsibly be made about how and where to allocate relief funds and what to do next.

Such data ought to flow easily and publicly from the Real Estate Board of New York, the Downtown Alliance or any of the brokerages that routinely churn out reams of statistics on the Class-B South Midtown sublease market.

Only one real-estate firm, Jones Lang LaSalle, has tried to tally the commercial toll. It found 29 percent of all of Downtown’s office space is still out of commission — nearly 30 percent of the area’s entire inventory.

But competitors say they’re wrong and the Real Estate Board dodges the question. One reason for uncertainty is that landlords and brokers refuse to share what they know with the public and the media, claiming they have to deal with their tenants first.

That won’t wash. Every large real-estate company has an army of numbers-crunchers who could assess the situation without interfering with business.

The silence from residential brokerages is even more shameful. Widely quoted analysts who can tell us how much unmarried female orinthologists spend on condo purchases have had zip to say about storm upheaval.

Yet the residential impact may prove worse than the commercial one. The loss of tenants and apartment owners who might not want to come back threatens Downtown’s transformed, family-friendly chemistry since 9/11.

My friends who’ve lived happily on West Street for years have no idea when they’ll be able to return. Residents of 2 Gold St. — an ultra-modern tower that opened just six years ago — have been told not to expect to return until March.

How many like them are there? Until those who ought to know do their jobs, Downtown will be as much in the dark as it was two weeks ago.